Editing Time signal (section)

=== Visual signals ===
[[File:Royal observatory greenwich.jpg|thumb|right|The [[time ball]] on the roof of [[Greenwich Observatory]], London]]
In 1861 and 1862, the Edinburgh Post Office Directory published time gun [[map]]s relating the number of seconds required for the report of the time gun to reach various locations in the city. Because [[speed of light|light]] travels much faster than [[speed of sound|sound]], visible signals enabled greater precision than audible ones, although audible signals could operate better under conditions of reduced visibility. The first [[time ball]] was erected at [[Portsmouth]], England in 1829 by its inventor [[Robert Wauchope (admiral)|Robert Wauchope]].<ref name=AUB>Aubin, David [https://books.google.com/books?id=9EKzLQL3RQEC&dq=Robert+Wauchope+time+ball&pg=PA164 The Heavens on Earth: Observatories and Astronomy in Nineteenth-Century Science and Culture] p.164. Duke University Press, 2010</ref> One was installed in 1833 on the roof of the [[Royal Greenwich Observatory|Royal Observatory]] in [[Greenwich]], London, and the time ball has dropped at 1:00 pm every day since then.<ref>{{cite web|url=http://wwp.greenwichmeantime.co.uk/info/timeball.htm|title=Greenwich Time Ball|website=greenwichmeantime.co.uk|access-date=8 April 2018|url-status=dead|archive-url=https://web.archive.org/web/20101023194034/http://wwp.greenwichmeantime.co.uk/info/timeball.htm|archive-date=23 October 2010}}</ref> The first American time ball went into service in 1845.<ref name=AUB/> In New York City, the ceremonial [[Times Square Ball]] drop on New Year's Eve in [[Times Square]] is a vestige of a visual time signal.